1. Technical Field
The present invention relates to a position adjustment amount calculation method of a light modulation device, a position adjustment amount calculation device of a light modulation device, a projector and the like.
2. Related Art
In recent years, a projector as a projection type image display device has been undergoing improvements in image quality and cost reduction, and there is demand for displaying high definition images in various scenes. For this reason, for example, in a liquid crystal projector having a plurality of liquid crystal panels (light modulation devices) corresponding to different color light beams, it is necessary to adjust installed positions of the liquid crystal panels with high accuracy such that images, which are formed using light beams modulated by the liquid crystal panels corresponding to the respective colors, accurately overlap with each other on a screen (projection plane). Therefore, it is important to precisely measure a position misalignment amount between the liquid crystal panels. Techniques for adjusting positions of such light modulation devices are disclosed in, for example, JP-A-2000-206633 and Japanese Patent No. 3757979.
JP-A-2000-206633 discloses a technique in which a position of one of liquid crystal panels provided for the respective colors is used as a reference, quantitative misalignment amounts of positions of the other liquid crystal panels are calculated, and the positions of the liquid crystal panels are adjusted. Here, in order to quantitate the misalignment amount, a method is used in which a test pattern is imaged by a camera (image capturing device), positions of the test pattern are calculated in the camera coordinates, and a difference between the positions of the test pattern, which are respectively obtained for two liquid crystal panels, is divided by the magnification of the camera.
Also, Japanese Patent No. 3757979 discloses a technique in which, in an image display device which displays images projected by a plurality of projectors by tiling, geometric correction for a superposed area is performed such that the images by the projectors are smoothly connected. At this time, in order to set correction parameters for the geometric correction, a correspondence relationship between positions of two projectors is specified using a camera. In order to measure the correspondence relationship, to begin with, a first correspondence relationship between camera coordinates and projector coordinates in a first projector is generated from a result obtained by the camera imaging three feature points (pixels or the like) which are displayed by the first projector (refer to paragraph 0038 in Japanese Patent No. 3757979). Next, a second correspondence relationship between the camera coordinates and projector coordinates in a second projector is generated from a result obtained by the camera imaging three feature points displayed by the second projector. In addition, a third correspondence relationship between the projector coordinates in the first projector and the projector coordinates in the second projector is generated from the first correspondence relationship and the second correspondence relationship.
However, there is a problem in the techniques disclosed in JP-A-2000-206633 and Japanese Patent No. 3757979 in that a degree of freedom in an installed position of the camera is low. For this reason, if the installed position of the camera is not precisely adjusted, there is a problem in that it is difficult to quantitate the position misalignment amounts of the liquid crystal panels with high accuracy. Hereinafter, this will be described using an example where a position misalignment amount between two liquid crystal panels, a first liquid crystal panel and a second liquid crystal panel is calculated.
FIG. 12A shows an example of a test pattern displayed on a screen using light which is modulated by the first liquid crystal panel. FIG. 12B shows an example of a test pattern displayed on the screen using light which is modulated by the second liquid crystal panel.
In FIG. 12A, the test pattern has four feature points (display pixels) P1 to P4. The feature points P1 to P4 are disposed such that the two points arranged in the transverse direction of a projection image IMG1 including the test pattern and the two points arranged in the longitudinal direction thereof form four corners of a rectangle. In FIG. 12B, the test pattern has one feature point (display pixel) Q1. Here, a pixel corresponding to the feature point P1 positioned at the upper left part among the feature points P1 to P4 in FIG. 12A and a pixel corresponding to the feature point Q1 in FIG. 12B are pixels located at the same positions in the respective liquid crystal panels.
FIG. 13A shows an example where the test pattern in FIG. 12A and the test pattern in FIG. 12B overlap with each other. FIG. 13B schematically shows a captured image obtained by imaging an area where the feature points exist in FIG. 13A using a camera. For example, the projection image IMG3 in FIG. 13A can be formed by a light synthesis means such as a cross-dichroic prism.
Here, the second liquid crystal panel is positioned so as to be misaligned with the first liquid crystal panel by the misalignment amount Δx=d of the projection image IMG3 in the transverse direction and the misalignment amount Δy=0 of the projection image IMG3 in the longitudinal direction, for the feature point P1 and the feature point Q1. Therefore, when an area AR0 surrounded by dotted lines in FIG. 13A is imaged by the camera, the captured image shown in FIG. 13B can be obtained. Thereby, since the misalignment amounts Δx and Δy are correctly calculated by the method disclosed in JP-A-2000-206633, it is possible to correctly adjust the position of either the first liquid crystal panel or the second liquid crystal panel according to the misalignment amounts Δx and Δy.
However, in the technique disclosed in JP-A-2000-206633, it is necessary to correctly install the camera imaging the area AR0 in FIG. 13A at a front-on position with respect to the screen. For example, if the camera is installed to be tilted, the misalignment amount may not be correctly calculated. In addition, in a case where an image passing through a projection lens constituting the projector is distorted, or the camera is installed to be shifted and tilted with respect to the screen as well, the misalignment amount may not be correctly calculated.
FIG. 14 schematically shows an example of a captured image obtained by imaging the area AR0 in FIG. 13A after the camera is fixed in a tilted state.
FIG. 15A schematically shows the distortion of an image projected by the projector. FIG. 15B schematically shows a captured image obtained by imaging the area AR0 in FIG. 15A using the camera. In FIGS. 15A and 15B, the parts corresponding to those in FIG. 13A have the same reference numerals.
FIG. 16 schematically shows a captured image obtained by imaging the area AR0 using the camera which is installed to be shifted and tilted with respect to the screen. In FIG. 16, the parts corresponding to those in FIG. 13A have the same reference numerals.
If an image is captured in the state where the camera is tilted, a captured image which is rotated relative to FIG. 13B can be obtained. For example, in the case of FIG. 14, the rectangle having the four corners of the feature points P1 to P4 is rotated relative to FIG. 13B. Therefore, it is necessary to calculate a misalignment amount between the feature point P1 and the feature point Q1 in consideration of the installed state of the camera, and there are cases where non-negligible errors occur in the calculated misalignment amount.
In the liquid crystal projector, images on the liquid crystal panels are displayed on the screen after passing through a projection lens. The images after passing through the projection lens are distorted, and an image actually displayed on the screen is similar to that shown in FIG. 15A. For this reason, in a captured image of the area AR0 in FIG. 15A, the rectangle having the feature points P1 to P4 as the four corners becomes the parallelogram as shown in FIG. 15B. In the method disclosed in JP-A-2000-206633, if the misalignment amount is calculated based on the captured image as shown in FIG. 14 or 15B, although the liquid crystal panel is actually misaligned only in the transverse direction, there are cases where the misalignment of the liquid crystal panel is considered to occur in the tilted direction as well. In this case, there is a problem in that the misalignment amount may not be correctly calculated.
At this time, a measurement error caused by the installation of the camera or a measurement error caused by the distortion of the projection lens may be solved to a degree through the measurement using the method disclosed in Japanese Patent No. 3757979. However, in the case where the camera is installed to be shifted and tilted with respect to the screen, in the captured image of the area AR0, the rectangle having the feature points P1 to P4 as the four corners does not even become the parallelogram. Thereby, there are problems in that it is difficult to correctly calculate a misalignment amount even using the method disclosed in Japanese Patent No. 3757979, and to correctly adjust positions of the liquid crystal panels.